Collaborative Research: Controls of ecosystem development during rapid environmental change: Yellowstone in the late-glacial and early-Holocene periods

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The period between the late-Pleistocene glacial maximum and the early-Holocene thermal maximum (ca. 21,000 to 7,000 years ago) was a time of dramatic environmental change and biotic adjustments. The creation of new ecosystems in deglaciated regions was governed by the rate of ice recession, the nature of postglacial climate change, the characteristics of new landscapes, and the life-history traits of the biologic colonizers.The Yellowstone region supported the largest independent ice field in the western U.S., and ice recession after 17 cal ka set in motion a sequence of poorly-documented biologic events that ultimately led to the present-day terrestrial and aquatic ecosystems. This examination of the late-glacial and early-Holocene periods in the Yellowstone region poses the following questions: What are the primary controls of terrestrial and aquatic ecosystem development on newly created landscapes? Specifically, how are past biota influenced by intrinsic biological constraints, landscape evolution, and subregional climate differences during a period of dramatic climate change? The study tests hypotheses concerning the importance of climatic and nonclimatic drivers in ecosystem development through an examination of lake-sediment records from sites that (1) lie along the path of ice recession, (2) span a variety of substrates, and (3) are situated within summer-wet and summer-dry precipitation regimes. Yellowstone is an ideal region to examine the development and structuring of terrestrial and aquatic ecosystems, because (1) the climate history of the western US is reasonably well understood from prior data syntheses and paleoclimate model simulations; (2) a well-documented glacial history of the Yellowstone region offers independent information on local environmental change; (3) different substrates and precipitation regimes shape modern ecosystem distributions and likely have in the past as well; and (4) previous paleoecologic findings motivate more-nuanced research questions that can be addressed with the acquisition of new high-resolution records.Intellectual Merit of the Research: Understanding the biotic consequences of climatic change is a major challenge in Earth systems research and identified as a high priority in recent international and US climate change assessments. The proposed study builds on existing knowledge of Yellowstone's past in an effort to better understand the resilience of terrestrial and aquatic ecosystems to environmental change, including abrupt climate events of the magnitude projected in the future. This project adopts a stratified sampling approach that is not possible in most locations where paleobiotic data are sparse, and the information gained will help answer basic biologic questions about the importance of abiotic and biotic variables in modulating the effects of climate change on species, communities, and ecosystems. The resulting synthesis will be a critical step in bridging the gap between current understanding of ecological processes on short time scales and evidence of dramatic change preserved in paleoecologic data on long time scales.Broader Impacts of the Research lie in its contribution to ongoing efforts that better inform the public, land and resource managers, and students about the importance of environmental history in the national parks, including an understanding of past climate change and ecosystem sensitivity. This project in particular, extends outreach activities in a number of ways, among them regularly updated web-disseminated information by the National Park Service on Yellowstone's history; education and training activities for Park staff on cutting-edge paleoclimate research; incorporation of Yellowstone findings in Park-directed K-12 curricula and university coursework; publication in popular scientific magazines; and content for a new museum exhibit on Yellowstone. The project also continues the PIs' commitment to train and educate the next generation of diverse scientists and to contribute to ongoing efforts to build multidisciplinary paleoclimate datasets for use by researchers, land managers, educators, and the public.